The present invention relates to a solar energy converter for converting solar energy emitted from the sun into electric energy.
Combustion of fossil fuels such as coal and petroleum for generating energy causes environmental issues worldwide. Further, fossil fuels are a limited natural resource. Thus, it is difficult to rely on fossil fuels as energy sources over the long term.
To resolve impending environmental issues as global warming and acid rain caused by carbon dioxide or nitrogen dioxide, which are generated by fossil fuel combustion, and to do away with apprehension of the imminent exhaustion of fossil fuels, it is necessary to develop a methodology and an apparatus that will efficiently convert solar energy. Development is indispensable for the survival of mankind. If the efficient conversion of solar energy into electric energy can be achieved, mankind can obtain a stable energy supply from the sun. Hence, various techniques relating to solar energy conversion have been diligently developed.
To foremost prerequisite in the methodology and apparatus for converting solar energy into electric energy is that it must be efficient. An associated requirement is that it must avoid using materials which may cause the destruction or deterioration of the environment, to make the best use of cleanliness of solar energy.
Another principal requirement is low cost manufacturing to enable widespread availability. To manufacture at low cost, materials, which are hard to obtain and high in a manufacturing cost, must be avoided. It is also desirable for the structure of the apparatus to be simple.
If the apparatus is simple, it is possible to use the apparatus for a long time with the replacement of the component parts. To use the apparatus for a long time, it is important that the apparatus has durability and a long operation-life. Further, it is desirable that maintenance and operational costs are low.
Further, it is desirable that the apparatus be lightweight and compact for use in many places.
Solar batteries using semiconductors are well-known, as an apparatus for directly converting solar energy into electric energy. In these conventional solar batteries, light wavelengths ranging from 400 nm to 450 nm in the vicinity of blue light are converted into electric energy, that is, only a part of the spectrum of sunlight is used. Namely, it is unattainable to convert all of the visible rays, from green to red, and infrared rays into electric energy in the conventional solar batteries. For this reason, many researchers have devoted themselves to increasing the efficiency of the solar batteries. However, it still remains, at best under 20%.
It is also known that semiconductors, which make up solar batteries, have high manufacturing costs and discharge materials that are environmentally unfriendly during manufacturing.
In the present circumstances, it is impossible to fulfill the above-mentioned requirements with the conventional methodologies and apparatuses.
It is a primary objective of the present invention to provide a solar energy converter which efficiently converts solar energy into electric energy by using a wide range of wavelengths from sunlight spectrum, including also a range of wavelengths which were not used for the conventional solar batteries, which can be manufactured at low cost, and which is environmentally friendly.
To solve the above-mentioned problems, the present invention is for providing a solar energy converter which uses an electron emitter unlike conventional solar batteries (PN connection semiconductor) that utilize only a part of sunlight spectrum.
The electron emitter is an electrode, which emits thermal electrons. In general, an electron emitter is produced by impregnating metals having high electron emission ability such as tungsten, tantalum, scandium, iridium or the like with materials easily emitting thermal electrons such as barium oxide, iridium oxide, strontium carbonate, a compound of iridium or scandium or the like, or by applying the materials on the metals. The electron emitter is a material emitting thermal electrons due to a rise in temperature, such as a carbon compound with a diamond structure, a carbon nanotube or a nitride-boron nanotube. The thermal electrons emitted from the electron emitter are captured and collected by an electron collector, and thereby the solar energy can be converted into electric energy.
An electron emitter was described in U.S. Pat. No. 3,358,178 in 1967, U.S. Pat. No. 3,719,856 in 1973 and U.S. Pat. No. 4,007,393 in 1977. These disclosures made it possible to enhance efficiency of thermal electron emission and improve durability. This kind of technique has been mainly used in the fields of vacuum tubes and CRTs (Cathode Ray Tube).
There is a phenomenon called electric field emission, where a potential barrier on the surface of a solid body, which holds electrons inside the body, becomes lower and thinner if a strong electric field is applied to the surface, and then the electrons are emitted into a vacuum by a tunneling effect.
In particular, if a material having a small radius of curvature is placed in the electric field, electric charges are concentrated on a pointed region with the small radius of curvature, and accordingly it facilitates electron emission. This is the so-called point-concentration phenomenon, and is well known in the field of electric discharge physics.
One characteristic of material with a diamond structure is that electrons can be emitted easily by the effect of negative electron affinity.
Materials such as a needle-shaped carbon, a carbon nanotube and a diamond thin film have been mainly used as an electric field emission material in the fields of vacuum tubes, fluorescent display tubes and electrical field emission displays (CRT, FED, VFD).
The structure of the solar energy converter in the present invention is partly similar to that of vacuum tubes. The functions of vacuum tubes are amplification, rectification and oscillation, while the function of this solar energy converter is electric generation. Consequently, the solar energy converter according to the present invention is completely different from vacuum tubes in respect of function.
Specifically, in accordance with the first aspect of the invention, the solar energy converter comprises:
a light-concentrating device for concentrating sunlight;
a heating plate provided in a vacuum vessel and irradiated with sunlight concentrated by the light-concentrating device;
an electron emitter, which is thermally connected to the heating plate, provided in the vacuum vessel for emitting electrons into a vacuum due to a rise in temperature of the heating plate;
an electron accelerator provided opposite to the electron emitter in the vacuum vessel;
an electron accelerating power source in which its negative terminal is connected to the electron emitter and its positive terminal is connected to the electron accelerator;
an electron deflector provided in the vacuum vessel for deflecting electron beam starting from the electron emitter; and
an electron collector for collecting the flying electrons deflected by the electron deflector,
wherein the electron collector is regarded as a negative electrode of the electric generator and the electron emitter is regarded as a positive electrode of the electric generator by moving electrons from the electron emitter to the electron collector, and thereby electricity can be generated.
In accordance with the second aspect of the invention, the solar energy converter comprises:
a light-concentrating device for concentrating sunlight;
a heating plate provided in a vacuum vessel and irradiated with sunlight concentrated by the light-concentrating device;
an electron emitter, which is thermally connected to the heating plate, provided in the vacuum vessel for emitting electrons into a vacuum due to a rise in temperature of the heating plate;
an electron accelerator provided opposite to the electron emitter in the vacuum vessel; an electron accelerating power source in which its negative terminal is connected to the electron emitter and its positive terminal is connected to the electron accelerator;
a first slit-type electron collector provided between the electron emitter and the electron accelerator for collecting flying electrons emitted from the electron emitter;
a second slit-type electron collector provided between the first slit-type electron collector and the electron accelerator in such a manner that the electric lines of force starting from the electron accelerator could pass through its slits; and
an electron deflector provided in the vacuum vessel for deflecting electron beam which passes through the slits of the first slit-type electron collector in such a manner that the second slit-type electron collector can capture and collect the flying electrons,
wherein the electron collector is regarded as a negative electrode of the electric generator and the electron emitter is regarded as a positive electrode of the electric generator by moving electrons from the electron emitter to the electron collector, and thereby electricity can be generated.
Further, in the solar energy converter according to the present invention, the electron deflector may comprise either a magnetic deflector or an electrostatic deflector.
Still further, in the solar energy converter according to the present invention, a surface of the electron collector may comprise metallic fibers or mesh-shaped or grid-shaped metal wires for capturing and collecting the flying electrons effectively.
In accordance with the third aspect of the invention, the solar energy converter comprises:
a light-concentrating device for concentrating sunlight;
a heating plate provided in a vacuum vessel and irradiated with sunlight concentrated by the light-concentrating device;
an electron emitter, which is thermally connected to the heating plate, provided in the vacuum vessel for emitting electrons into a vacuum due to a rise in temperature of the heating plate;
an electron accelerator provided opposite to the electron emitter in the vacuum vessel;
an electron accelerating power source in which its negative terminal is connected to the electron emitter and its positive terminal is connected to the electron accelerator; and
an electron collector provided between the electron emitter and the electron accelerator for collecting flying electrons emitted from the electron emitter,
wherein the electron collector comprises metallic fibers or mesh-shaped or grid-shaped metal wires, and the electron collector is regarded as a negative electrode of the electric generator and the electron emitter is regarded as a positive electrode of the electric generator by moving electrons from the electron emitter to the electron collector, and thereby electricity can be generated.
In accordance with the fourth aspect of the invention, the solar energy converter comprises:
a light-concentrating device for concentrating sunlight;
a heating plate provided in a vacuum vessel and irradiated with sunlight concentrated by the light-concentrating device;
an electron emitter, which is thermally connected to the heating plate, provided in the vacuum vessel for emitting electrons into a vacuum due to a rise in temperature of the heating plate;
an electron accelerator provided opposite to the electron emitter in the vacuum vessel;
an electron accelerating power source in which its negative terminal is connected to the electron emitter and its positive terminal is connected to the electron accelerator; and
an electron collector provided between the electron emitter and the electron accelerator for collecting flying electrons emitted from the electron emitter,
wherein the electron accelerator and the electron collector are electrically insulated from each other, and the electron collector is regarded as a negative electrode of the electric generator and the electron emitter is regarded as a positive electrode of the electric generator by moving electrons from the electron emitter to the electron collector, and thereby electricity can be generated.
In the solar energy converter according to the present invention, the electron emitter may contain or may be coated with a compound which comprises at least one selected from the group consisting of iridium, scandium, barium and carbon.
In the solar energy converter according to the present invention, the electron collector may comprise one selected from the group consisting of stainless, molybdenum compound, tungsten compound and the like.
In the solar energy converter according to the present invention, at least one of two things may be processed to be a blackbody: the heating plate and the electron emitter.
In the solar energy converter according to the present invention, the electron collector may include an electron-leakage preventing member to prevent the electrons from being reflected from the collector after collision against the electron collector.
In the solar energy converter according to the present invention, the electron collector may be curved in such a manner that the center of its curvature is located on the side of the electron emitter.
In the solar energy converter according to the present invention, a sunlight penetration window may be formed in a partial region of the vacuum vessel to allow sunlight concentrated by the light-concentrating device to pass through the vacuum vessel.
In the solar energy converter according to the present invention, the heating plate may be fixed to the vacuum vessel by means of a fixing member made of a non-thermally conductive material.
In the solar energy converter according to the present invention, an insulator may be sandwich between the heating plate and the electron emitter disposed in the vacuum vessel.
In accordance with the fifth aspect of the invention, the solar energy converter comprises:
a cathode and an anode provided opposite to each other in a vacuum vessel;
an electric field generating power source provided for generating an electric field between the cathode and the anode by connecting its negative terminal to the cathode and its positive terminal to the anode;
an electron emitter capable of passing through the electric field, provided between the cathode and the anode in the vacuum vessel, for emitting electrons into a vacuum due to sunlight heat; and
an electron collector capable of passing through the electric field, provided between the electron emitter and the anode in the vacuum vessel, for collecting the electrons emitted from the electron emitter,
wherein the electron collector is regarded as a negative electrode of the electric generator and the electron emitter is regarded as a positive electrode of the electric generator by moving electrons from the electron emitter to the electron collector, and thereby electricity can be generated.
In accordance with the sixth aspect of the invention, the solar energy converter comprises:
a cathode and an anode provided opposite to each other in a vacuum vessel;
an electric-field generating power source provided for generating an electric field between the cathode and the anode by connecting its negative terminal to the cathode and its positive terminal to the anode;
an electron emitter capable of passing through the electric field, provided between the cathode and the anode in the vacuum vessel, for emitting electrons into a vacuum due to sunlight heat;
a first slit-type electron collector provided between the electron emitter and the electron accelerator for collecting flying electrons emitted from the electron emitter;
a second slit-type electron collector provided between the first slit-type electron collector and the electron accelerator in such a manner that the electric lines of force starting from the electron accelerator could pass through its slits; and
an electron deflector provided in the vacuum vessel for deflecting electron beam having passed through the slits of the first slit-type electron collector to allow the second slit-type electron collector to collect the flying electrons,
wherein the electron collector is regarded as a negative electrode of the electric generator and the electron emitter is regarded as a positive electrode of the electric generator by moving electrons from the electron emitter to the electron collector, and thereby electricity can be generated.
In accordance with the seventh aspect of the invention, the solar energy converter comprises:
a cathode and an anode provided opposite to each other in a vacuum vessel;
an electric field generating power source provided for generating an electric field between the cathode and the anode by connecting its negative terminal to the cathode and its positive terminal to the anode;
an electron emitter capable of passing through the electric field, provided between the cathode and the anode in the vacuum vessel, for emitting electrons into a vacuum owing to a rise of temperature;
an electron deflector provided in the vacuum vessel for deflecting electron beam starting from the electron emitter; and
an electron collector provided for collecting electron beam which is deflected by the electron deflector,
wherein the electron collector is regarded as a negative electrode of the electric generator and the electron emitter is regarded as a positive electrode of the electric generator by moving electrons from the electron emitter to the electron collector, and thereby electricity can be generated.
In the solar energy converter according to the present invention, an insulator may be provided on the anode side of the electron collector.
In the solar energy converter according to the present invention, a sunlight penetration window for sunlight passing through the vacuum vessel may be formed in a partial region of the vacuum vessel in such a manner that the electron emitter can be irradiated with sunlight.
Further, the solar energy converter according to the present invention may be also provided with a light-concentrating device for concentrating sunlight in such a manner that the electron emitter can be irradiated with sunlight concentrated by the light-concentrating device.
Still further, in the solar energy converter according to the present invention, the light-concentrating device may be provided with either a lens or a concave mirror.
In the solar energy converter according to the present invention, at least the electron emitter out of the electron emitter and the electron collector may comprise a material containing carbon compound.
In the solar energy converter according to the present invention, at least the electron emitter out of the electron emitter and the electron collector may comprise a material having a diamond structure.
In the solar energy converter according to the present invention, at least the electron emitter out of the electron emitter and the electron collector may comprise a carbon nanotube.
In the solar energy converter according to the present invention, either the electron emitter or the electron collector may be provided with a fiber-shaped, or mesh-shaped, or grid-shaped conductive member.
In the solar energy converter according to the present invention, the electron emitter may comprise one selected from the group consisting of a material made of carbon, a material having a diamond structure and a carbon nanotube, and the electron collector may comprise one selected from the group consisting of a material made of carbon, a material having a diamond structure and a carbon nanotube, and these materials may be combined in the electron emitter and electron collector.
In the solar energy converter according to the present invention, the electron collector may comprise one selected from the group consisting of stainless, molybdenum compound and tungsten compound.
In the solar energy converter according to the present invention, the electron deflector may comprise either a magnetic deflector or an elector-static deflector.